Rakdos lord of riots

[Kona6]

Someone told me his cost reduction ability is set depending on how much life your opponent lost the turn  {Rakdos, Lord of Riots} is brought out and does not change? I'm pretty sure I changes turn by turn depending on life lost by the opponent, he was very certain he was correct though. Which is right though? Please help with this...

Ex : he hits me for 9 damage. Brings out rakdos.
Do his creatures cost 9 less to cast forever?

[Maximo]

No. It resets at the end of every turn.

[Kona6]

Ah so I was right . Thank you

[Hays413]

Man some people come up with some weird rulings. Punch that guy for being dumb.